#include <string>

using namespace std;

class Solution
{
public:
    int romanToInt(string s)
    {
        int ret = 0;
        int prenum = getNum(s[0]);
        for (int cur = 1; cur < s.size(); ++cur)
        {
            int num = getNum(s[cur]);
            if (prenum >= num)
            {
                ret += prenum;
            }
            else if (prenum < num)
            {
                ret -= prenum;
            }
            prenum = num;
        }
        ret += prenum;
        return ret;
    }

    int getNum(char num)
    {
        switch (num)
        {
        case 'I':
            return 1;
        case 'V':
            return 5;
        case 'X':
            return 10;
        case 'L':
            return 50;
        case 'C':
            return 100;
        case 'D':
            return 500;
        case 'M':
            return 1000;
        default:
            return 0;
        }
    }
};